The invention relates to a microwave vector modulator provided with a transmission line, to an input of which microwave radiation can be applied, and adjustable reflection means for adjustably reflecting at least part of the microwave radiation applied to the input.
The invention also relates to a device for the matching of a microwave load comprising a microwave source, a microwave load, a transmission line through which microwave radiation generated by the microwave source is applied to the microwave load, a vector modulator incorporated in the transmission line, with which an adjustable part of the microwave radiation generated by the microwave source can be reflected, and a quadrature detector to which at least part of the microwave radiation reflected by the microwave load and vector modulator is applied and to which also part of the microwave radiation generated by the microwave source is applied, whereby the quadrature detector controls the vector modulator so that a closed loop is obtained with which the microwave radiation reflected by the microwave load and vector modulator is cancelled out.
A vector modulator and its application in a device for cancelling reflections at a microwave load are known from the contribution of P. D. L. Beasley et al. at the International Radar Conference 1990, Washington. Mr. Beasley describes a CW radar installation which employs a single antenna for simultaneous transmitting and receiving. This necessitates the use of a vector modulator which in a closed loop compensates for reflections of microwave radiation at the antenna. It should be noted that actually it is not matching of a microwave load that is at issue here, but the prevention of reflections from penetrating into the receiver branch.
This solution permits a low-power vector modulator to be employed, whose internal losses can practically be ignored.